The role of the innate immune system in pulmonary fibrosis, remains imperfectly understood. In other systems it is established that components of the innate immune system shape the more precise response of the adaptive immune system. Using a well described animal model of subacute pulmonary inflammation and fibrosis, the role of two of the Toll-Like Receptors, major components of the innate immune sytem and the specific influence each has on T lymphocyte differentiation, will be examined. Specifically, Aim 1 will describe the role of TLR2 in turning T cells away from a protective Th1 pathway of development, and Specific Aim 2 will demonstrate the role of TLR4 in producing T regulatory cells that protect from lung injury. Pulmonary fibrosis is the end stage of a wide range of diverse diseases, and leads to progressive respiratory failure and death. Currently understanding of why this occurs, and how to stop this process, is very limited, and better understanding will allow more useful therapies.